The present invention relates to a fingerprint input apparatus and, more particularly, to a fingerprint input apparatus capable of directly reading a fingerprint image using a two-dimensional image sensor.
In a conventional fingerprint input apparatus of this type, the skin surface of the fingertip is irradiated with light at a predetermined angle using optical components such as a lens and prism or a fiber. The light reflected by the skin surface is focused to output a fingerprint image. Alternatively, a study has been made on a scheme of directly inputting a fingerprint image using an electrostatic capacitance instead of obtaining a fingerprint image using the optical system.
In these conventional fingerprint input apparatuses, when the optical components such as a lens and prism or a fiber are used, a space for the sizes of these optical components and their mounting positions is required to result in a large thickness and size of the apparatus. In addition, since these optical components are relatively expensive, the apparatus cannot be manufactured at low cost. When the fingerprint image is optically processed using these optical components, the resultant image tends to distort.
The scheme of directly inputting a fingerprint image using the electrostatic capacitance is susceptible to external static electricity and difficult to obtain a high sensitivity.
It is an object of the present invention to provide a relatively low-profile, compact, inexpensive fingerprint image input apparatus.
It is another object of the present invention to provide a fingerprint image input apparatus capable of obtaining an image free from distortion.
In order to achieve the above objects of the present invention, there is provided a fingerprint input apparatus comprising scattered light generated inside a finger having a fingerprint pattern in accordance with external light, the fingerprint pattern being made up of a ridge portion and a valley portion, and a two-dimensional image sensor made of a large number of light-receiving elements arranged in a two-dimensional array, an image of the fingerprint pattern being input to a light-receiving surface of the light-receiving element, wherein the light-receiving element whose light-receiving surface is in substantially contact with the ridge portion detects as the ridge portion a bright portion where the scattered light emerging from the finger reaches at a high intensity, and the light-receiving element whose light-receiving surface corresponds to the valley portion via a space detects as the valley portion a dark portion where the scattering light emerging from the finger reaches at a low intensity.